The goals of this project for the next fiscal year are: (1) To advance significantly in the study of soluble antigens associated with MTV to determine the incidence, diagnostic value and immunologic implications for solid tumors; (2) To continue the study of the relationship of naturally occurring antibodies to the host susceptibility, incidence of these antibodies and immunogenetic influence on tumor incidence; (3) To identify one or more tumor or viral specific antigens from human breast tumors; and (4) To study the question of whether animal oncogenic viruses play a discernible role in human leukemia or breast cancer.